The multiracial Boxx, whose biological father, was black, was raised by her white single mother in Southern California. In a 2008 interview, she remembered that she had little contact with her African American heritage until she went to Notre Dame:[5]

“

For me, I really learned about my other half. I took African American studies. I majored in it. I think that was one of the best things I could have ever done. My mom couldn't teach me those things. So I went and taught myself and learned those things when I was at Notre Dame.

From U/12-U/18,[6] Boxx played for the Torrance United Waves Soccer Club, Torrance, California, and helped to lead them to 4 State Cup Championships and two trips to the USYSA National Championship Final Four in 1993 and 1994[7][8] at U/17 and U/19.

From 1991 to 1995, Boxx attended South Torrance High School, where she was a four-sport athlete, playing soccer, volleyball, softball and basketball. She was named to the Parade All-America team for girls' soccer in 1995.[9]

In the 2001 season, Boxx started all 21 matches for the Spirit, missing 20 minutes of the entire season, and was named to the All-WUSA team.[10] However, her playing time was reduced the following season, and in September 2002, she was sent to the New York Power, in a six-player trade that gave San Diego the first overall pick in the 2003 draft, used to select Aly Wagner.[11]

With New York, Boxx returned to form, starting all 21 games, scoring once and assisting a career-high eight times, and was named to the 2003 All-WUSA squad.[12] Former women's national team coach and league commissioner Tony DiCicco called Boxx "the best in our league at (defensive midfield) – physical, strong, technical".[10]

In 2009, Boxx signed to the Los Angeles Sol for the inaugural season of Women's Professional Soccer and was named team captain. She started in 18 of the 19 matches she played for the Sol, scoring three goals with three assists. Boxx was named to the WPS First Team and played in the WPS All-Star Game. The Sol finished in first place during the regular season with a 12–3–5 record.[9]

Later in the season after Saint Louis Athletica folded, she was traded to the FC Gold Pride.[14] Boxx helped the team win the WPS regular season title and championship. She started in 19 of the 20 games she played in, while scoring one goal and providing five assists. She was a WPS All-Star Game starter and received the fifth overall votes.[9]

For the 2011 WPS season, Boxx signed with magicJack and played 833 minutes in 10 games starting in them all. She helped the club make a run to the playoffs in the second half of the season and win the quarterfinal match against the Boston Breakers.[9]

In 2013 she joined Chicago Red Stars in the new National Women's Soccer League. Due to injury Boxx played 2 matches in 2013, played in 5 matches in 2014 due to pregnancy and birth of her first child, and in 2015 played 4 times due World Cup duties. On July 27, 2015, Boxx announced retirement from NWSL and Red Stars effective immediately.[15]

Boxx scored a goal in each of the two pre-World Cup friendlies, against Costa Rica and Mexico, and in the opening match of the World Cup against Sweden, Boxx became the first American woman to score three goals in her first three matches with the national team.[10]

Boxx started five matches at the Women's World Cup, scoring again against Canada in the third place match. She was voted the player of the match against Canada by the FIFA Technical Study Group, who said Boxx "seized control of the game, spurred on her team-mates and finally scored the decisive goal in USA's victory".[4]

Boxx started 31 of 32 national team matches she played in 2004, including all six matches at the 2004 Olympics, where she scored a goal, assisted on another and helped the team win a Gold Medal.[9] She scored eight goals over the course of the year, including a hat trick against Trinidad and Tobago in an Olympic qualifying match. Boxx came in seventh in the voting for the 2004 FIFA World Player of the Year award.

Boxx missed most of 2006, first for surgery to repair torn cartilage in her right hip, and then for torn medial collateral ligaments she suffered on her first day back in training with the national team.[17] She returned in 2007 after an eight-month layoff, and was named to the United States' squad for the 2007 FIFA Women's World Cup. Boxx helped the team reach the semifinal match against Brazil, but she was sent off after receiving two yellow cards, and the United States went on to lose 4–0.[18] Boxx played every minute of all five U.S. games in the 2008 Summer Olympics in Beijing.

In 2011 she played in all but one of the world cup games, earning defensive team honors for her efforts throughout the tournament. During the World Cup final against Japan, which went to overtime penalty shoot-out, Boxx was one of the Americans elected to take one of the penalty kicks, and had her shot saved by Japan's goalkeeper.[19]

Geographic location of the venue where the competition occurred
Sorted by country name first, then by city name

Lineup

Start – played entire matchonminute (offplayer) – substituted on at the minute indicated, and player was substituted off at the same time

offminute (onplayer) – substituted off at the minute indicated, and player was substituted on at the same time
(c) – captain
Sorted by minutes played

#

NumberOfGoals.goalNumber scored by the player in the match (alternate notation to Goal in match)

Min

The minute in the match the goal was scored. For list that include caps, blank indicates played in the match but did not score a goal.

Assist/pass

The ball was passed by the player, which assisted in scoring the goal. This column depends on the availability and source of this information.

penalty or pk

Goal scored on penalty-kick which was awarded due to foul by opponent. (Goals scored in penalty-shoot-out, at the end of a tied match after extra-time, are not included.)

Score

The match score after the goal was scored.
Sorted by goal difference, then by goal scored by the player's team

Result

The final score.

Sorted by goal difference in the match, then by goal difference in penalty-shoot-out if it is taken, followed by goal scored by the player's team in the match, then by goal scored in the penalty-shoot-out. For matches with identical final scores, match ending in extra-time without penalty-shoot-out is a tougher match, therefore precede matches that ended in regulation

aet

The score at the end of extra-time; the match was tied at the end of 90' regulation

pso

Penalty-shoot-out score shown in parenthesis; the match was tied at the end of extra-time